Michael Phelps, the most decorated Olympian in history and the face of US Swimming since 2004, has seen Ledecky train and compete for years and said she is in a class of her own.

"She's someone that's very goal-oriented," Phelps said while speaking to Business Insider. "When she writes a time down or she writes a major milestone down, she's gonna do whatever she can to make sure that happens. I've only seen that really a couple times in the sport. So it's a true treat for me to be able to see her kind of truly coming up in the sport like she is."

After a strong World Championships performance and freshman year at Stanford, Ledecky is poised to have a strong showing at the 2020 Tokyo Olympics. The 2020 Olympics will now include the 1,500-meter freestyle for the first time, a race in which Ledecky currently holds the world record. Phelps said with such a busy slate, Ledecky could have the chance to win seven or eight medals.

"Ledecky has just been on fire the last couple of years," Phelps said.

However, there's also a drawback to that. Asked about the possibility of Ledecky one day challenging Phelps' medal record, Phelps said it takes almost perfect conditions to win so many events.

"When you start building a program like that, when you're swimming seven or eight races, it's just a combination of everything — mental, physical, emotions — that really have to be pretty much perfect throughout that whole eight-day program," Phelps said.

Still, Phelps said he would love to see someone like Ledecky challenge his record.

"I would love to see it, I would enjoy watching it, and I hope somebody has that chance to make history again."